Napkin Math

Napkin Math is a personalized food journal that pairs a photo-based log with an AI nutrition coach. Snap a picture of a meal and the app figures out the macros, then tailors guidance to a user's actual schedule — marathon training, office lunches, social dinners — instead of pushing a generic calorie deficit.

The team is part of Y Combinator's Spring 2026 batch and is led by Manuel Castro, Claire Nord, and Jynnie Tang. It ships on iOS, Android, and the web.

Free to download, with the headline pitch being a journal that 'people love to use' — useful for anyone whose previous tracker died after a week of typing in food names by hand.